1. Field of the Invention
The present invention relates to a fixation device for mounting a hand tool to a drill template when cutting a hole in an object, and, more particularly, a fixation device used with a drill template and a hand tool for cutting a hole that has a larger diameter than the diameter of the cutting tool.
2. Description of the Related Art
When machining materials using a portable or hand tool, many advantages are achieved due to the flexible positioning of the tool and degrees of freedom of motion of the tool with respect to the workpiece. The advantages of using a portable or hand tool include the ability to position the tool in positions not allowed by a stationary tool, overhead for example, or to position the tool and machine a workpiece that is part of a larger assembly, such as may occur during a repair operation. Machining a workpiece with a curved (or other non flat geometry) surface can be made easier with a portable or hand tool due to the inherent positioning flexibility.
Additionally, templates are used in conjunction with machine tools to easily replicate a workpiece pattern. When using templates the machine tool is guided by the template pattern requiring the motion of the machine tool to be constrained by the template pattern. The use of a template with a portable or hand tool can be problematic due to the inherent positioning flexibility and degrees of freedom of motion of the tool which now must be constrained to follow the template pattern.
U.S. Pat. No. 5,641,252 (Eriksson et al.) discloses a method for machining holes in a fiber reinforced composite material by using at least one cutting tool with wear resistant surface positioned eccentrically in relation to a central axis. The material is machined simultaneously in both an axial and a radial direction by causing the tool to move axially while rotating not only about its own axis, but also eccentrically about the central axis. In accordance with one feature of the invention, the workpiece is oriented in such a way that the axis of rotation of the tool is essentially orthogonal in relation to the longitudinal directions of the fibers in the immediate vicinity of the point where the tool meets the working surface. The diameter of the cutting tool is substantially smaller than the diameter of the hole that is produced. The eccentric rotary motion is generally a strictly rotary motion, i.e., it is executed with a constant distance between the central axis and the axis of rotation of the cutting tool. This distance between the central axis and the axis of rotation of the cutting tool can be increased by linear increments as the eccentric rotary motion continues.
This known method has a number of substantial advantages as compared with generally familiar techniques. For example, the method permits the production of holes without strength reducing damage. Also, the method permits the production of holes free from damage without having to preform a hole. Further, the method permits the production of holes to tight tolerances. The dimensional accuracy of the hole is determined substantially by the accuracy of the positioning of the tool relative to the central axis. The requirements imposed on the geometry of the cutting tool are not particularly high, on the other hand, since every individual tool is simply calibrated before use. Additionally, the method prevents the tool from becoming blocked. Since the diameter of the tool is substantially smaller than that of the hole, the method permits material removed by cutting to be carried away by simple means, such as with compressed air. The method also permits effective cooling of the tool and the edge of the hole. Yet another advantage is that the method substantially reduces the cost of wear compared to previously disclosed methods, due to the tool being coated with a wear resistant material, such as diamond coating. Moreover, this method also offers advantages when machining other materials such as metals.
U.S. Pat. No. 6,382,890 (Linderholm) discloses a hand tool apparatus using a cutting tool to machine a hole in an object such that the hole has a width at least as large as the width of the cutting tool. The center line of the hole passes through a predetermined point on the surface of the object. Moreover, the disclosed invention provides a compact and lightweight hand tool apparatus for machining holes in a flat or curved object of any material by rotating a cutting tool about its own axis and about a principal axis while simultaneously feeding in the axial direction. A lightweight and compact apparatus is achieved by integrating a radial offset mechanism, spindle motor and axial feed mechanism in a same actuating assembly package, which rotates about a principal axis.
Template machining is well known in the art when using a machine tool to replicate an object or pattern in a workpiece. A template is used to consistently guide a machine tool during the machining operation and thereby simplify the process. A hand tool apparatus as disclosed in U.S. Pat. No. 6,382,890 (Linderholm) has advantages over a fixed machine tool in terms of flexibility and more degrees of freedom in motion and positioning; however, these same advantages can create difficulty in maintaining the proper orientation of the hand tool apparatus with respect to the template and workpiece during the machining operation. This difficulty may be particularly evident during an orbital drilling process when the tool is subjected to both an axial force and a radial force through the cutting tool tip by virtue of machining simultaneously in both an axial and radial direction.
What is needed in the art is a method and device for maintaining the orientation of a hand tool apparatus with respect to the template and during the machining process.